Cliff Grays Podcast with Aaron Davidson

[Stinky Coyote]

Whoa, take a day or two off and like Christmas! Let’s goooo

Aaron, you’re up

 

[grfox92]

Oh man, I just dont know when I'll have the time to get through this massive dissertation.

Sent from my SM-G990U using Tapatalk

 

[Deadspace]

@Aaron Davidson, maybe I misheard this but are you offering the new Endex in 6 creedmoor? I don’t see that option on your website.

 

[grfox92]

@Aaron Davidson, maybe I misheard this but are you offering the new Endex in 6 creedmoor? I don’t see that option on your website.

Im pretty sure they will chamber whatever you want.

Sent from my SM-G990U using Tapatalk

 

[Clark33]

Geez, the guys railing against Aaron and calling him a "douche" sound a bit...."douchey" themselves.

His experiences with the NX8's and MK5's really got my attention.

EDIT: I don't own a GW, but I appreciate the innovation for our sport

 

[Aaron Davidson]

@Aaron Davidson, maybe I misheard this but are you offering the new Endex in 6 creedmoor? I don’t see that option on your website.

Its not a published option online, but you can order via phone.

 

[wind gypsy]

They don't stay locked up. The axial preload you can max without yielding is less than the force generated by the cartridge expansion on firing that is opposite the thread preload.

Maybe someone can help me understand this.. If you cant pre-load to a force higher than the force of a round going off without yielding, why doesn't the force of the round going off cause the joint to yield? Only thing i can think of is that the pre-load is primarily on the first few threads but in the opposite direction the force can be split amongst all the threads?

 

[BBob]

If you cant pre-load to a force higher than the force of a round going off without yielding, why doesn't the force of the round going off cause the joint to yield?

But isn't that what is happening? The force of the round is causing the joint to yield (move). Isn't that what Vaughn shows and what Aaron is saying?

Only thing i can think of is that the pre-load is primarily on the first few threads

And that is exactly how threads in a std threaded joint is. Only the first few threads carry most of the load.

Std threaded joint, ramp threaded joint (Spiralock) and a variable depth (tapered) threaded joint.

 

[wind gypsy]

But isn't that what is happening? The force of the round is causing the joint to yield (move). Isn't that what Vaughn shows and what Aaron is saying?


And that is exactly how threads in a std threaded joint is. Only the first few threads carry most of the load.

Std threaded joint, ramp threaded joint (Spiralock) and a variable depth (tapered) threaded joint.

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I was looking at yielding as the thread failing.

 

[BBob]

I was looking at yielding as the thread failing.

I think we’re a long ways from catastrophic thread failure unless you do something really dumb to cause it.

As to the joint moving this was tested ad nauseam years ago in the benchrest world in both long and short range. The conclusion was it didn’t matter in at least the BR PPC cases. As far as I know no one is doing anything special in LRBR for some of the larger WSM range cases either. It might be interesting to see or hear about what the ELR crowd is doing or thinks about it. I’ve never kept up with that group.

 

[wind gypsy]

I think we’re a long ways from catastrophic thread failure unless you do something really dumb to cause it.

What is meant by preloading to the point of yielding then? Like it's tightened so much the headspace has "yielded" to be too short? These maybe dumb questions, trying to wrap my head around it.

 

[Sundodger]

Maybe someone can help me understand this.. If you cant pre-load to a force higher than the force of a round going off without yielding, why doesn't the force of the round going off cause the joint to yield? Only thing i can think of is that the pre-load is primarily on the first few threads but in the opposite direction the force can be split amongst all the threads?

Because the forces you are speaking of are going in opposite directions.

This is over simplified, but think of it this way:
-When you are done tightening the action to barrel there is a residual tensile load "pulling" the action and barrel together.
-If the force from service (in this case the round going off) that is pushing the action and barrel apart meets the residual tensile load pulling the action and barrel together, they cancel out.

That means you have zero clamp load in your joint and it can unthread.

You need substantially more residual load keeping a joint together than it will see in service, for reasons that will get us off in the weeds.

 

[BBob]

What is meant by preloading to the point of yielding then? Like it's tightened so much the headspace has "yielded" to be too short? These maybe dumb questions, trying to wrap my head around it.

Are you referencing Aaron’s statement?

“The axial preload you can max without yielding is less than the force generated by the cartridge expansion on firing “.

If so I would have to think that yes at some point the threads will start to pull, fail from overloading when initially assembling the joint. A threaded joint can only be loaded to a certain point before it will fail or start to fail. We’ve all stripped threaded bolts and screws by over tightening or at least I have

 

[wind gypsy]

Are you referencing Aaron’s statement?

“The axial preload you can max without yielding is less than the force generated by the cartridge expansion on firing “.

Yes, that's what i'm referencing. If the pre-load forces needed to avoid yielding during firing would cause thread failure, why is it no where close to thread failure during firing? Or if i'm misinterpreting, what is meant by yielding with enough pre-load?

If so I would have to think that yes at some point the threads will start to pull, fail from overloading when initially assembling the joint. A threaded joint can only be loaded to a certain point before it will fail or start to fail. We’ve all stripped threaded bolts and screws by over tightening or at least I have

 

[BBob]

If you would have to go past thread failure to have enough pre-load,

You can’t go beyond that point which I think is his point. If you need more pre load to stabilize the joint you’ll have to re-design the joint. He’s also pointing out that the commonly sized and or designed joints used in rifle actions are inadequate for larger magnum cartridges at least for an accuracy standpoint.

I think you’re confounding a joint not being strong enough or stable enough to resist moving to a joint not having enough strength to not fail. The current used joints are plenty strong enough to resist failure in normal use but will move under certain conditions such as what Aaron is stating.

 

[Aaron Davidson]

If you try to increase the pre-load to a point that it is greater than the "separating" forces, you will yeild. Eg strip threads, or the face of the action/barrel, or the recoil lug (which ever is the softer material and/or lowest surface area).

Sundodger nailed the other concept.

 

[Sundodger]

I was looking at yielding as the thread failing.

Thread failing is just one of many potential failure modes. The action or bolt (barrel in this case) enter the plastic deformation region of their stress/strain curve (just after the yield point) is what Aaron was hinting at.

Once past the yield strength point on the curve, materials start "necking down" which often (but not always) is what we are trying to avoid. An example of when we intentionally plastically deform the fastener is torque to yield head bolts on many engines, but that is for very different reasons.

Look up stress strain curve on Wikipedia, it has a good overview on tensile testing.

 

[wind gypsy]

Appreciate all of you guys 'learnin me.

There is a similar discussion going on right now over at snipershide in a thread started by a guy saying 100 fl/lb tq on prefits is stupid and they shouldn't need more than 35. Some good and interesting contributions by industry folks.

• Mike R of TacOps weighed in saying he torques to 300+, sometimes substantially more depending on action and he referenced Vaughn's book.
• Ern who does prefits for Altus i believe said he uses 70 ft/lb and indicated he does put much stock in Ted of ARC's input because he cant hold a headspace tolerance
• Owner of PVA figured Ern had the wrong spec and said the spec he had and cuts CDG prefits to is 0.003" longer than what Ern referenced and ARC has published on their site for CDG headspace spec
• Owner of PVA recommends 70 for standard bolt face and 100 for magnums and provided some calculations to justify it (responding to my questions that mimicked some in this thread). However, he indicated the pre-load with the above torque values exceeded the force of the rounds being fired.

Barrel Torque Ludicrocity

lol. Really though. 100ftlbs for prefit barrel torque? ****, I know this isn’t necessary. AR15 armorer schools is min 35ftlbs unless old school barrel nut needs advanced to next cut out for gas tube clearance. Then it’s 35-65ftlbs range. I run 55ftlbs on my bolt gun Savage style barrel nut...

www.snipershide.com

 

[JohnJohnson]

Appreciate all of you guys 'learnin me.

There is a similar discussion going on right now over at snipershide in a thread started by a guy saying 100 fl/lb tq on prefits is stupid and they shouldn't need more than 35. Some good and interesting contributions by industry folks.

• Mike R of TacOps weighed in saying he torques to 300+ and he referenced Vaughn's book.
• Ern who does prefits for Altus i believe said he recommends 100 ft/lb and said he doesn't much faith in Ted of ARC's input because he cant hold a headspace tolerance
• Owner of PVA stood up to defend Ted and indicated he cuts all of his CDG prefits to a spec that is 0.003" off from what ARC has published on their site for CDG headspace spec
• Owner of PVA recommends 70 for standard bolt face and 100 for magnums and provided some calculations to justify it (responding to my questions that mimicked some in this thread). However, he indicated the pre-load with the above torque values exceeded the force of the rounds being fired.

Barrel Torque Ludicrocity

lol. Really though. 100ftlbs for prefit barrel torque? ****, I know this isn’t necessary. AR15 armorer schools is min 35ftlbs unless old school barrel nut needs advanced to next cut out for gas tube clearance. Then it’s 35-65ftlbs range. I run 55ftlbs on my bolt gun Savage style barrel nut...

www.snipershide.com

Small addition, I asked TS Customs and they use 100 ft/lbs for their torque.

 

[BBob]

Just to add info: When you tighten common action/barrel thread joints to the same torque spec but use different thread TPI's (16,18, 20 tpi) the amount of rotation of the barrel before full lockup at that torque are all noticeably different. Basically when fitting/timing fluted barrels you have to account for different amounts of rotation per the tpi used in that joint at a specified or desired torque. What is better? I don't have an opinion on that as they all work.

I'll add that anything north of 100ft lbs starts to rapidly get harder and harder to hold without slippage. Not impossible but that's about the point where I've found it to start to noticeably change and where you might need a good insert type barrel vise over something like a Viper style.